1. Field of the Invention
The present invention relates, generally, to friction devices, such as clutch or brake assemblies for use in transmissions, differentials, or brake systems. More specifically, the present invention relates to multiple-clutch or -brake assemblies.
2. Description of the Related Art
Friction devices are employed in a wide range of applications as clutches or brakes. For example, such friction devices are frequently used in land-based vehicles. Generally speaking, land-based vehicles require three basic components. These components include a power plant (such as an internal-combustion engine), a powertrain, and wheels. The powertrain""s main component is typically referred to as the xe2x80x9ctransmission.xe2x80x9d
Engine torque and speed are converted in the transmission in accordance with the tractive-power demand of the vehicle. Transmissions include one or more gear sets, each of which may include an inner sun-gear, intermediate planet-gears supported by their carriers, and outer ring-gears. Various components of the gear sets are held or powered to change the gear ratios in the transmission.
The multi-disk pack clutch is a friction device that is commonly employed as a holding mechanism in a transmission or differential. Other multi-disk friction devices, such as wet brakes, also find use in industrial applicationsxe2x80x94for example, to brake the wheels on earth-moving equipment.
The multi-disk pack clutch or brake assembly has a clutch sub-assembly that includes a set of plates and a set of friction disks, the plates and friction discs being interleaved between one another. The plates and friction disks are bathed in a continual flow of lubricant and, in xe2x80x9copen packxe2x80x9d operation, normally turn past one another without contact. Such clutch or brake assembly also typically includes a piston. When a component of a gear set is to be held, as, for example, during a particular gear range, a piston is actuated so as to cause the plates and friction disks to come into contact with respect to one another.
In certain applications, it is known to employ several multi-disk pack friction devices in combination to establish different drive connections throughout the transmission or differential to provide various gear ratios in operation or to brake a component. In double-clutch assemblies, for instance, one of the clutches is used for starting-up, and both clutches are used for shifting into intermediate gears.
German Patent DE 35 26 630 A1 discloses a double clutch adapted to be applied to a gear for changing the speed of a motor vehicle. To that end, two clutches alternately couple a central shaft and a hollow shaft that is concentric with the central shaft. Specifically, a disk of the clutch connected to the central shaft and a disk of the clutch connected to the hollow shaft can be pressed against a plate of a revolving-clutch casing.
German Patent DE 43 32 466 A1 discloses a double multi-disc clutch that encloses a powered, revolving casing. Each inner-disk assembly of the two clutches is torsionally fixed to a different center member. One center member is torsionally fixed on a shaft, and the other center member is torsionally fixed on a hollow shaft that is concentric with the other shaft such that one clutch surrounds the other, thereby reducing axial-design space.
The double-clutch assemblies described above having concentric shafts can be advantageously used with auxiliary-range transmissions. In particular, the shifting thrust during gear changes can be minimized or eliminated, and an interruption in propulsive power can be avoided.
However, multiple-clutch assemblies of the kind described above need improvement. Among other things, they cannot be used in and combined with a large number of transmission types and designs. In addition, numerous auxiliary unitsxe2x80x94such as oil pumps, filters, oil containers, sensors, solenoid valves, control-valve assemblies, electronic controlsxe2x80x94are distributed across the entire transmission.
Thus, there is a need in the art for a multiple-clutch assembly that forms an extensive, self-sufficient unit; can be easily combined with transmissions of different designs and sizes; and reduces design space, weight, and manufacturing costs.
The present invention overcomes the disadvantages in the related art in a clutch assembly including a housing and a first clutch having a first drive member rotatably supported within the housing on a drive hub and a first driven member rotatably supported within the housing on a first driven shaft. A first clutch pack is interposed between the first drive and driven members and operable to selectively connect and disconnect the first drive and driven members for transferring and interrupting torque between the first drive and driven members.
A second clutch is supported within the housing coaxial with respect to the first clutch and includes a second drive member rotatably supported within the housing on the drive hub and a second driven member rotatably supported within the housing on a second driven shaft. The first and second driven shafts are disposed concentrically relative to one another. A second clutch pack is interposed between the second drive and driven members and operable to selectively connect and disconnect the second drive and driven members for transferring and interrupting torque between the second drive and driven members.
A torsional damper is connected between a source of power and the drive hub, thereby dampening torsional vibrations between the source of power and the first and second clutches.
Accordingly, one advantage of the present invention is that an extensive, self-sufficient multiple-clutch assembly is provided that can be easily combined with transmissions of different designs and sizes.
Another advantage of the present invention is that most, if not all, of the most important auxiliary units of a transmission can be incorporated within the present invention.
Another advantage of the present invention is that a modular constructional multiple-clutch assembly is provided that can be completely pre-manufactured, assembled, and tested.
Another advantage of the present invention is that it can be used with manual transmissions.
Another advantage of the present invention is that an especially large, effective centrifugal mass is created through a torsionally-fixed union of one of two centrifugal masses of the torsional damper and a bell, including its components, of one of the two clutches.
Finally, these advantages are achieved in a multiple-clutch assembly that reduces design space, weight, and manufacturing costs.
Other features and advantages of the present invention will be readily appreciated as the same becomes better understood after reading the subsequent description when considered in connection with the accompanying drawings.